Join Us On

An Encyclopædia Britannica Company

Dictionary

Thesaurus

Medical

Scrabble^®

Spanish Central

Browse Dictionary Browse Thesaurus

Get our free apps!iPhone•iPad•Android

Dictionary

mos

abbreviation

Definition of MOS

months

MOS

abbreviation

Definition of MOS

1

metal-oxide semiconductor

2

military occupational specialty

Browse

Next Word in the Dictionary: mosaic (noun)Previous Word in the Dictionary: morulaAll Words Near: mos

Seen & Heard

What made you want to look up mos? Please tell us where you read or heard it (including the quote, if possible).

View Seen & Heard Highlights from Around the Site

Test Your Vocabulary!

10 Charming Words for Nasty People

Put-downs with flair

Learn More

When "Literally" isn't, well, literal

How to use a word that (literally) drives some people nuts.

Watch Now

Know what this is?

Test your vocab with our fun, fast game

Go Play

Fear of cats?

Ailurophobia, and 9 other unusual fears

Learn More

Join Us

Merriam-Webster
on Facebook

Merriam-Webster
on Twitter

Bookstore: Digital and Print

Merriam-Webster references for Mobile, Kindle, print, and more.

See All

Other Merriam-Webster Dictionaries